Sustainable surface transport

at intermediate speed the diesel equivalent specific fuel consumption (BSFC) is below 205 g/kWh and at rated speed (4000 rpm) below 235 g/kWh.

The corresponding values for the effective efficiencies are 41.4% (intermediate speed) and 36.2% (rated speed). Compared to a Ü=1 state-of-the-art CNG engine fuel consumption is improved up to 15%.

There is a great potential to realize a lean burn CNG engine with Diesel equivalent fuel consumption if further research work is done on the improvements of the combustion process by high in-cylinder peak pressure, advanced boosting system in combination with/without EGR and NOx aftertreatment devices. NOx reduction only by the measure of high air excess requires relative air/fuel ratios above 1.6 in combination with retarded ignition timings to reach borderline the Euro 4 limit for light duty vehicles (250 mg/km). Due to the NOx-effective retarded ignition timing the advantage regarding fuel consumption is in the range of 5% compared to stoichiometric operation (Euro 4). Of course CO emission is not critical in the lean operation mode. Compared to stoichiometric operation, the raw THC emission increases by approximately 100%. To reach the hydrocarbon Euro 4 limit the necessary conversion rate of the oxidation catalyst is more than 95%. To achieve the Euro 5 emission standards a NOx-aftertreatment device is required.
In Internal Combustion Engines there is a general trend towards the increase of the power density through the downsizing + turbocharging. Thanks to the higher octane number of methane, such an approach should be fully exploited by natural gas engines with two main advantages:

the achievement of an extra benefit in terms of fuel conversion efficiency with the development of a new generation of engines which will be able to provide an efficiency significantly higher than the 2006 diesel engine;

a higher impact on the customer because providing a level of vehicle performance equal to that of today vehicles powered by engines running on conventional liquid fuels, because the fun-to-drive characteristics of the present naturally aspirated (NA) bifuel OEM vehicles, when running on gas mode, are very far from the actual market standards.

Then the higher power density of natural gas vehicles has to be implemented taking into account the specific technology way adopted by each sub-project.

Enabling technologies of the three technology ways are:
Assessment of the natural gas quality;

On-board storage of gas tanks;

Development of an ad hoc aftertreatment system.
Enabling Technology A. In 1996 the project BRPR-CT96-0213 填se of NG Passenger Cars Components for Bi-fuel Vehicles and Concepts to Handle Varying Gas Compositions (NG COMPONENTS & FUELS)coordinated by BMW took care of the relationship between the natural gas quality and the NG components. This study as well other studies on the subject carried out in Europe by the OEMs (as, for instance, Fiat) opened the way to the today marketed CNG bi-fuel vehicles. However, there is a lack of knowledge about the quality of gaseous fuels and associated detection systems. For the first time the following actions are performed:

a detailed survey of the different types of the natural gas (including biogas) that is available in Europe to create the basis for reliable control strategies ensuring an optimal engine operation;

innovative strategies for detecting gas property and development of the additional sensors dedicated to gas property measurement;

use of upgraded biogas (biomethane) and natural gas and hydrogen (H2) as a fuel.

Enabling Technology B. In 1997 the pioneer project BRPR-CT96-0337 鏑ow emission vehicle with integrated natural gas storage system (LEVINGS)provided a deep insight of different ways to store on-board natural gas. Besides safety in use (covered by the ECE R 110 regulation) and the highest possible capacity for that given external envelope, NG tanks should achieve the best compromise between three conflicting requirements: to be inexpensive, light and safe. In terms of mass /volume ratio (i.e. mass of the cylinder without gas and the cylinder volume as water capacity), the today steel cylinders are characterized by an average figure of 0.9 kg/l, while the composite cylinders with metal and polyethylene liners can arrive to a mass/volume ratio of 0.5 and 0.3 kg/l respectively. The most difficult task is to develop an automotive storage system able to guarantee to the driver a mileage comparable with that of the gasoline vehicle. The project proposes an innovative solution for on-board fuel storage which enables a significantly extended driving range with respect to current solutions, the aim being to provide 500 km of autonomy, with acceptable weight, dimensions and costs.
Enabling Technology C. Two main technology gaps hinder the development of an efficient CH4 abatement by the exhaust gas aftertreatment:

an ignition temperature for methane oxidation substantially lower than that of presently available catalysts;

an exhaust thermal management and an exhaust process design optimized to provide a catalyst temperature range allowing full methane conversion without the risk of temporary high temperature excursions.

The main drawback of present three-way catalyst (TWC) systems consists in forcing the engine first into conditions of high exhaust temperatures (for rapid catalyst heat-up) and later by keeping the catalyst at this temperature level. The today exhaust catalyst train is replaced by a counterflow heat exchanger reactor unit where the catalyst is situated at the hot side of the heat exchanger. A separate small fuel burner provides hot gas for a rapid cold start of the unit. As soon as the right part is hot enough, the cold gas entering the heat exchanger is heated up by the hot gas leaving the heat exchanger. In this way about 80% of the heat introduced by the burner or liberated in the TWC can be recovered, i. e. transferred to the entering exhaust gas. This means that the additional fuel requirement for heating the exhaust up to e. g. 500 ｰC is reduced down to about 20% compared to the amount required without heat recovery. Besides fuel economy, a substantial advantage of this concept over the state of the art, is the fact that the catalyst thermal management is decoupled from engine management and that the catalyst needs no longer to be split into an engine-close pre-cat and a main catalyst.

Of the two concepts for NOx aftertreatment under lean conditions, NOx storage catalyst (NSC) with periodic regeneration events and SCR catalyst with a urea tank and injection device, for small and mid-size engines (< 2 liter displacement, typical of CNG engines), the most competitive with regard to the cost is the NSC. It is however not clear, if a NSC regeneration by a transient rich spike is viable at all, due to the stability and the low reactivity of the methane molecule. However under rich conditions the reactivity could be enhanced through the steam reforming reaction, leading to the generation of hydrogen as highly active molecule for the regeneration of a NSC. Therefore, a major task is the evaluation of the possibility of a NSC regeneration by rich exhaust of a CNG engine.

1.3 S/T methodology and associated work plan

1.3.1 Overall strategy of the work plan
The objective of the Collaborative Project 的ntegrated gas powertrain (InGas)is to deploy a custom designed engine integrated with specific aftertreatment systems applied to a light duty (LD) vehicle able to achieve a 10% higher fuel conversion efficiency than that of a corresponding 2006 diesel vehicle and complying with an emission level lower than Euro 6. Additional features are advanced storage systems and vehicle architectures, as well as multi-grade fuel tolerance and fuel flexibility. The overall implementation plan (Fig. 1.2) gives an overview of the activities defined in the collaborative project InGas.

Fig. 1.2 ｨC Overall implementation plan of InGas. The combustion process/engine development for Üハ=1 (SPA1), ハÜΟΓハフハハÜ> 1 ｨC with stratified approach - (SPA2), Üハ>> 1 ｨC around/higher 1.35 with homogenous approach ｨC (SPA3) is supported by the development of enabling technologies for Fuels (SPB0), Storage (SPB1) and Aftertreatment (SPB2).

To achieve the InGas targets of Tables 1.2 and 1.3, the horizontal Sub-Projects B0, B1 and B2 will provide the three enabling technologies to the vertical Sub-Projects A1, A2 and A3 comparing the three technology ways.: Strong interactions exist among all the Sub-Projects, both horizontal and vertical (see Fig. 1.2). The Table of paragraph 1.3.5 迭isk identification and contingency plansdetails the potentials risks & corrective actions for each Sub-Project.
At first the three horizontal sub-projects providing the enabling technologies should be examined.
The aim of Sub-Project B0 擢uels for advanced CNG enginesis the definition and the supply the gas mixture of the requested quality to the other sub-projects. In doing such an activity the sub-project B0 will conduct analyses and propose solutions in order to affect in a flexible way storage, combustion, aftertreatment and performance of the CNG vehicles. A first milestone is the supply of gas mixtures that have to be supplied according to a strict schedule to the partners (WP B0.3); a second important milestone is the development of a methodology able to identify, via gas sensors, the gas quality, that, taking into account variations in gas composition, can guarantee the requested fuel flexibility of Table 1.2 to the advanced CNG engines (WP B0.5). An essential objective of the Sub-Project B0 is the assessment of Well-to-Tank (WtT) performance of the different gaseous mixtures necessary to establish the overall Well-to-Wheel (WtW) balance based on Tank-to-Wheels (TtW) assessment resulting from the three different technology ways (WP B0.6). Then the work-package B0.6, outcome of the collaborative project with the integrated CNG system assessment, is led by the project coordinator (CRF) and will verify the achievements of targets shown in Table 1.3.
The aim of Sub-Project B1 敵as storage for passenger car CNG engineis the development of advanced gas storage and filling systems including specific components and gas sensors, in correspondence with the target of achieving a vehicle range in the more than 500 km (Table 1.2). This target requires the possibility to develop advance storage system components (WP B1.3) and highly integrated storage module fulfilling all automotive constraints, e.g. weight, volume, costs, assembly/disassembly, maintenance and safety requirements (WP B1.4); such a possibility will be verified by appropriate milestones. The design analysis on the gas storage system will be validated with numerical simulations of different crash load cases, essential to develop advanced CNG vehicle concepts (WP B1.5).
The Sub-Project B2 鄭ftertreatment for passenger car CNG enginedeals with the development of an aftertreatment system for natural gas vehicles having special regards to CH4 conversion efficiency and NOx abatement under lean combustion operations. It is not only a matter of achieving a high CH4 conversion efficiency (> 90% on 160.000 km with lower cost than today catalyst as shown in Table 1.2), but also of developing the innovative catalyst system able to support the completely different combustion approaches of the three technology ways of Sub-Projects A1, A2 and A3 in achieving the pollutant emission targets without any undue penalty of fuel conversion efficiency (Table 1.3). In such a work, the Sub-Project deserves more than one critical work-package and associated milestone:

WP B2.2 鄭dvanced catalyst developmentwhere a no suitable catalyst formulation, identified with regard to low light-off temperature (< 330ｰC), requires a further development of current Pd-technology with increased PM-content or/and engine measures or/and enhanced focus on heat exchanger technology for increasing the exhaust temperature cause of increase in cost and fuel consumption. Another risk, affecting in particular the necessary input to Sub-Projects A2 and A3, could be represented by a NOx storage catalyst (NSC) technology for NOx removal not suitable for CNG lean application due to poor NO/SOx-regeneration efficiency with methane; this requires a corrective action based on the alternative DeNOx technology like urea-SCR (Selective Catalytic Reduction) with increase of complexity and cost.

WP B2.3 摘xhaust Heating/Catalyst Conceptswhere, if the coating of heat exchanger with catalyst wash-coat is not successful, an alternative concept based on serial arrangement of heat exchanger and catalyst brick shall be studied; the drawback is the increase in system volume and loss in catalytic efficiency.

WP B2.4 摘ngine testing / Exhaust Aftertreatment (EAT) managementand WP B2.5 摘AT system integration / optimizationrequiring the demonstration of catalyst long-term durability and the proper engine bench packaging respectively.

The aim of Sub-Project A1 鼎NG technologies for passenger carsis the development of a natural gas car powered by a 1.4 liter displacement engine by adopting the innovative technology of variavle valve management on stoichiometric combustion / sequential multi-point port gas injection approach. After the base engine development (WP A1.1), the development and calibration of the engine control system (WP A1.2) and the combustion process investigation (WP A1.3) will allow to obtain projections on vehicle performance (fun-to-drive), emissions and fuel consumption to be compared with targets of Tables 1.2 and 1.3. This first milestone will take into account the corrective actions, if any, necessary to meet the targets. Other actions deal with the aftertreatment development in conjunction with Sub-Project B2 (WP A1.4) and the carefull study of the gas system integration into the vehicle (WP A1.5) as requested by target of Table 1.2.
The aim of Sub-Project A2 典urbo DI CNG engineis the development of a natural gas car powered by a 1.8 liter displacement engine by adopting the innovative technology of direct gas in-cylinder injection for stoichiometric and stratified lean burn approach with (in the case of stratified combustion a very high air excess ratio lambda is achievable). After the definition of the engine layout (WP A2.1), a particular care will be devoted to the development (WP A2.2) and hardware procurement (WP A2.3) of a gas injection system that for performance, injector stability and size is compatible with the selected engine. A first milestone will take into account if corrective actions in terms of injector positioning on the selected engine or need to change the engine have to be introduced. A second milestone associated to the lean combustion system development (WP A2.4) and the transient engine testing (WP A2.5) will allow to verify if the targets of Tables 1.2 and 1.3 can be achieved or the proper corrective actions (see paragraph 1.3.5) if targets are not fulfilled.
The aim of Sub-Project A3 釘oosted lean burn gas engineis the development of a natural gas light-duty vehicle powered by a 1.9 liter displacement engine adopting an innovative over-boosted ultra-lean combustion system, i.e. able to achieve an air excess ratio lambda between 1.35 and 1.6, using port gas injection (at first) or low pressure direct gas injection (if the port gas injection is not sufficient). After a first phase of concept phase and design specifications (WP A3.1), the engine components procurement (WP A.3.2) will carefully consider the balance between components specifications and costs. The milestone associated with testing of components, engine and powertrain (WP A3.3) will take into account the possibility to achieve on the multi-cylinder engine the targets in terms of vehicle performance (Table 1.2) and fuel conversion efficiency and emissions (Table 1.3) based on Single Cylinder Engine (SCE) tests; actions on two-stage turbocharging system, engine-out emissions able to be controlled by the lean aftertreatment considered in Sub-Project B2 and implementation of powertrain functionalities into the control unit.
The Sub-Projects A1, A2 and A3 are different not only for the basic approach of the given technology way, but also for the engine size and typer of application: 1.4 liter displacement engine for a passenger car (A1), 1.8 liter displacement engine for cars (A2) and 1.9 liter displacement for a light commercial vehicle (A3). All the Sub-Projects dealing with the three technology ways end with a work package devoted to the assessment of the overall targets achieved by each technology way. The Sub-Project A3 is the more risky one: here, the last work package (A3.4) what will be the balance between the different targets of Tables 1.2 and 1.3; if there are just poor results for reduction of emissions or efficiency or if the driveability is not acceptable, the calibration only can be improved to reach two or one target(s). The outcome of the Sub-Projects Ai is interpreted via the Tank-to-Wheels (TtW) assessment of natural gases of different quality and gaseous fuel mixtures including biogas and hydrogen with natural gas (SP B0). All the three Sub-Projects Ai represent the ultimate research effort to realize a gas light-duty vehicle reaching the best compromise between market expectations of Table 1.2, EU Community targets of Table 1.3 and costs, that at the end will decide about the exploitation of the research.
Sub-project A1 鼎NG technologies for passenger cars”

A. State of the art of the technology involved in sub-project A1 (SPA1)

The very high knocking resistance of natural gas allows to achieve higher compression ratios (11 i 13) and a much higher optimum spark advance (15ｰ i 25ｰ) than those of gasoline with a significant gain in fuel conversion efficiency. The high oxidation resistance explains the lower laminar flame velocity of methane against all other hydrocarbons in the Ü range of 0.7 i 1.3. The lower laminar flame velocity of methane (33.8 cm/s) with respect to gasoline (38 cm/s) is reflected by the 10% i 11% lower burn rate of natural gas than that of gasoline inside the engine cylinder at the same turbulence level. The inherently combustion stability of the NG engine can be fully exploited at Ü equal to 1. When operated with natural gas the air excess ratio Ü is always equal to 1 to optimize, with a stoichiometric A/F ratio, performance, exhaust gas temperature before catalyst and emissions, while Ü of the gasoline engine in the peak torque region is lower than 1 (rich mixture) to achieve the optimum performance. At the optimum spark advance, the NG engine shows from 5 to 20% higher fuel conversion efficiency under the steady-state operations than the gasoline engine. This difference is even higher (- 20% - 30% as a fuel consumption) if the real city driving of the vehicle is considered, since the gasoline engine needs more fuel during cold starting and warm-up, and requires a Ü lower than 1 during dynamic transient operations. Nevertheless, the today stoichiometric CNG vehicle needs more advanced technologies to improve its fuel conversion efficiency to a level that should be even lower than that of a diesel engine.

B. Innovative character of SPA1 with respect to the state-of-the-art and its quantitative ambitious objectives

SP A1 is focussed on the integration of the natural gas technologies onto the new engine generation in order to realise a high power density / high efficiency powertrain unit with an application size target corresponding to a C-segment vehicle, which will be used as validator platform in the final part of the project.
Considering the technological innovative contents of the subproject, the aim is the development of a 4 cylinders 1.4 liter turbocharged engine equipped, from the air path side, with an innovative electronic control of the intake air, and, from the fuel metering side, with a dedicated management of the A/F ratio able to fulfil the ambitious target in terms of pollutant emissions but also to provide a higher fuel conversion efficiency. Within this context, the areas of development for innovative solutions will be:

the engine distribution system equipped with the electronic actuation of the inlet valve: the system is able to ensure a cycle-by-cycle regulation of the air at the inlet, thus providing the capability to manage transient operations with a simultaneous control of the A/F ratio. The direct control of the air provided by the inlet valves is also a key point for the increase of the engine efficiency at part load, conditions that typically affect the spark ignited engines in comparison to diesel ones.

the engine lay out in terms of compression ratio determination vs supercharging ratio, which is fundamental for the efficiency / pollutant determination : a dedicated combustion chamber geometry will be studied in order to optimize the combustion process with specific attention to combustion stability under wide open throttle conditions where a lean burn approach will be also evaluated.

the engine turbocharging system, expressly developed for the specific A/F control : the need for an increase in fun to drive feeling and to high thermal efficiency at full power means to be able to have high turbocharging efficiency in very wide range of flow rate taking into accounts also the lower temperature level attended with Natural Gas.

the exhaust aftertreatment system, which has to take into account the introduction of turbocharging and high thermal efficiency which will be translated into a temperature decrease at the exhaust, which is not in favour for the catalyst light ｨC off; innovative solutions will be developed and tested in order to increase especially the methane conversion at low temperatures but also to ensure at the same time a backpressure level which will not affect the engine efficiency.

the engine control system which will be able to manage a multiple new functionalities, including also the capability to adapt the regulation parameters to the gas fuel composition also taking into account the use of natural gas + hydrogen blends. The use of this kind of blend represents an additional step in the reduction of both pollutant emissions and CO2 formation. Apart from the 渡aturalextra reduction of the CO2 emissions due to the increase of the H/C ratio of the fuel, hydrogen represents a flame propagation booster which could provide an additional gain to the thermodynamic efficiency. Moreover a reduction in THC emissions is also expected taking into account the reduction of the flame quenching phenomena in the crevices of the combustion chamber.

Table A1.1 Specific targets of subproject A1 for 1.4 liter displacement car belonging to the C segment (General targets in Tables 1.2 and 1.3)

State of the art

TargetMax power density ~ 45 kW/l> 65 kW/lMax torque density~ 85 Nm/l> 130 Nｷm/lCO2 emission on NEDC test cycle~ 150 g/km< 130 g/kmC. Concise description of the work-packages (WPs) of SPA1

The resulting mixing from the partnership shows a clear focus on the optimization of the combustion process and on the aftertreatment system, which are key points for the general pathway of the sub-project. In this way, the development activities will be supported by intensive modelling simulations and experimental activities devoted to screen and indicate the right solutions to transfer to the following step of development.

WP A1.1 Base Engine Development ｨC The objective is to determine the optimum engine lay out in order to fulfil project targets in terms of fuel economy and pollutants emission. An important content of innovation is represented by the "multiair" system, which has been conceived to control the intake air flow cycle by cycle; for its integration into the engine a specific activity is needed in order to define the camshaft profile, the electric equipment and the preliminary calibration of the multiair subsystem at the lab rig. The determination of some other key components, such as the turbocharger group and the engine compression ratio, will be done by means of engine simulations with the use of the AMESim code. In the last task, the engines needed for CRF experimental activities will be build up.

WP A1.2 Engine control system development and calibration ｨC The HW of the engine control system has to be determined considering specific input/output interfaces related to CNG/engine system components; once the configuration frozen, the prototype ECU needed for the experimental activities will be built up.